Ohyamashimo Formation
Geologic formation in Japan
From Wikipedia, the free encyclopedia
The Ohyamashimo Formation(大山下層) is an Early Cretaceous (Albian) geologic formation, distributed in Tamba and Tamba-Sasayama, Hyogo Prefecture, Japan. It has been dated to the early-mid Albian, between 112.1 ± 0.4 Ma and 106.4 ± 0.4 Ma. The depositional environment represents a fluvial system with a subhumid to semi-arid climate. The Ohyamashimo Formation was called the 'Lower Formation' of the Sasayama Group before it was named in 2017.[1]
| Ohyamashimo Formation | |
|---|---|
| Stratigraphic range: Albian ~ | |
Type locality of the Tambatitanis, currently covered by concrete for protection. | |
| Type | Geological formation |
| Unit of | Sasayama Group |
| Underlies | Sawada Formation |
| Overlies | Basement (Unconformity) |
| Thickness | 1300 metres |
| Lithology | |
| Primary | Conglomerate, Sandstone, Mudstone |
| Other | Tuff |
| Location | |
| Coordinates | 35.1°N 135.1°E |
| Approximate paleocoordinates | 47.9°N 132.8°E |
| Region | Hyōgo Prefecture |
| Country | Japan |
| Type section | |
| Named for | Ohyamashimo, Tamba-Sasayama |
| Named by | Hayashi et al., 2017[1] |
  Ohyamashimo Formation (Japan) | |
Fossil content
Color key
|
Notes Uncertain or tentative taxa are in small text; |
Dinosaurs
Ornithischians
| Ornithischians of the Ohyamashimo Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Ankylosauria Indet.[2] | Indeterminate | Kamitaki Bonebed Quarry, Tamba | Albian | Dental remains. | ||
| Iguanodontia Indet.[2] | Indeterminate | Kamitaki Bonebed Quarry, Tamba | Albian | Dental remains. | ||
| Sasayamagnomus[3] | S. saegusai | Miyada microvertebrate site, Tamba-Sasayama | Albian | Skull elements and partial postcranial remains. | A neoceratopsian; closely related to Aquilops americanus. |  |
Saurischians
Sauropods
| Sauropods of the Ohyamashimo Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Tambatitanis[2] | T. amicitiae | Kamitaki Bonebed Quarry, Tamba | Albian | A single partial skeleton. | A titanosauriform sauropod |  |
Theropods
Indeterminate theropod dental remains are known from the Kamitaki Bonebed Quarry, Tamba.[2]
| Theropods of the Ohyamashimo Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Hypnovenator[4] | H. matsubaraetoheorum | Nishikosa, Tamba-Sasayama | Albian | A single partial skeleton. | A troodontid theropod; closely related to Gobivenator mongoliensis. |  |
| Therizinosauria Indet.[2] | Indeterminate | Kamitaki Bonebed Quarry, Tamba | Albian | Dental remains. | ||
| Tyrannosauroidea Indet.[2] | Indeterminate | Kamitaki Bonebed Quarry, Tamba | Albian | Dental remains. | ||
Squamates
| Squamtes of the Ohyamashimo Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Morohasaurus[5] | M. kamitakiensis | Kamitaki Egg Quarry, Tamba | Albian | A nearly complete left dentary. | A monstersaurian lizard |  |
| Pachygenys[6] | P. adachii | Miyada microvertebrate site, Tamba-Sasayama | Albian | A single, partially broken right mandible | A scincomorphan lizard |  |
Amphibians
| Amphibian of the Ohyamashimo Formation[7] | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Hyogobatrachus | H. wadai | Kamitaki Bonebed Quarry, Tamba | Albian | A nearly complete skeleton. | A frog |  |
| Tambabatrachus | T. kawazu | Kamitaki Bonebed Quarry, Tamba | Albian | An articulated skeleton lacking the anterior part of the skull, most of the pectoral girdle, manus, and feet. | A frog |  |
Mammals
| Mammals of the Ohyamashimo Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Sasayamamylos[8] | S. kawaii | Miyada microvertebrate site, Tamba-Sasayama | Albian | Three dentaries. | A asioryctitherian eutherian |  |
Crustaceans
| Crustaceans of the Ohyamashimo Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Mongolocypris | M. sp. | Albian | A ostracod | |||
| Conchostraca Indet. | Indeterminate | Albian | A clam shrimp | |||
Molluscs
Bivalves
Gastropods
| Gastropods of the Ohyamashimo Formation | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Viviparus | V. cf. keishoensis | Albian | A viviparid gastropod | |||
Oofossils
| Eggs of the Ohyamasimo Formation[9][10] | ||||||
|---|---|---|---|---|---|---|
| Genus | Species | Location | Stratigraphic position | Material | Notes | Images |
| Elongatoolithus | E. sp. | Kamitaki Bonebed Quarry, Tamba | Likely laid by oviraptorosaur. | |||
| Himeoolithus | H. murakamii | Kamitaki Egg Quarry, Tamba | Likely laid by a small theropod. | |||
| Nipponoolithus | N. ramosus | Kamitaki Bonebed Quarry and Kamitaki Egg Quarry, Tamba | Likely laid by non-avian maniraptoran theropod. | |||
| Prismatoolithus | P. sp. | Kamitaki Bonebed Quarry and Kamitaki Egg Quarry, Tamba | Likely laid by either troodontids or birds. | |||
| Subtiliolithus | S. hyogoensis | Kamitaki Bonebed Quarry and Kamitaki Egg Quarry, Tamba | Likely laid by a small theropod. | |||
| Spheroolithus | S. sp. | Kamitaki Bonebed Quarry, Tamba | Likely laid by hadrosaurs or other ornithopods. | |||